A262519 Odd bisection of A155043.

1, 2, 3, 4, 3, 4, 5, 5, 6, 7, 7, 8, 6, 9, 10, 11, 11, 12, 13, 13, 14, 15, 14, 15, 10, 16, 17, 17, 18, 19, 20, 19, 21, 22, 22, 23, 24, 23, 25, 26, 15, 16, 16, 17, 18, 18, 19, 19, 20, 20, 21, 22, 21, 22, 23, 23, 24, 24, 24, 25, 21, 26, 22, 23, 23, 24, 24, 24, 25, 26, 26, 27, 27, 27, 28, 29, 28, 30, 31, 31, 32, 33, 32, 33, 28, 33, 34, 29, 35, 36, 37, 37

Offset

0,2

Comments

Number of steps needed to reach zero when starting from k = 2*n + 1 and repeatedly applying the map that replaces k by k - d(k), where d(k) is the number of divisors of k (A000005).

Links

Antti Karttunen, Table of n, a(n) for n = 0..10000

A. Karttunen, Ratio a(n)/A262518(n) drawn with the help of OEIS Plot2-script

Formula

a(n) = A155043(2*n + 1).

Mathematica

Table[Length[NestWhileList[#-DivisorSigma[0, #]&, n, #!=0&]]-1, {n, 1, 200, 2}] (* Harvey P. Dale, Aug 31 2017 *)

Prog

(Scheme) (define (A262519 n) (A155043 (+ n n 1)))

Crossrefs

Cf. A000005, A049820, A155043, A262518, A262520, A262521, A262681.

Sequence in context: A307531 A125619 A349946 * A225320 A308937 A123066

Adjacent sequences: A262516 A262517 A262518 * A262520 A262521 A262522

Keyword

nonn

Author

Antti Karttunen, Oct 02 2015

Status

approved